Mobile communications involve the exchange of radio frequency (RF) signals between a mobile device and a base station. When these RF signals are blocked or degraded, a call placed to the mobile device cannot be completed or connected, because the base station is unable to establish a communication link to the mobile device in response to a call origination request from another communications device. The base station may be unable to establish the communication link to the mobile device for various reasons. For example, the control signals for call setup that are transmitted from the base station to the mobile device may be blocked, reflected, absorbed, or attenuated before they reach the mobile device.
When a base station is unable to establish a communication link to a recipient mobile device, the recipient device will not ring. Thus, it will not provide any indication to its user that it had failed to connect with an incoming call as a result of poor coverage, unless a user of an originating communications device leaves a voicemail or a callback number (when prompted to do so by a pre-recorded carrier message). If the user of the originating device decides to not leave a voicemail or a callback number, her other option may be to try calling again in a few minutes. However, she may simply forget to call again altogether. In that situation, the user of the recipient device may never know that he had missed a call from the user of the originating device.